An apparatus for turning workpieces moved forward in a flat position is already known from German patent DE 23 04 642. In this prior art apparatus, the workpieces are engaged at their centreline parallel to the original front edge at a position near to the side edge, with the possibility of turning at this point, and then moved along by frictional lock with one bearing surface until completion of preferentially a 90.degree. turn perpendicular to the original front edge. For this purpose, two conveying chains circulating in synchronisation are provided in a vertical plane, and these are provided with spaced, interacting clamping elements which are rotatable around axes perpendicular to the plane of motion and which serve to engage the workpieces. According to this apparatus, the workpieces are moved into position laterally and then held at the point of rotation. Because of the friction with the bearing surface of the table, the laterally protruding area of the workpiece drags behind the rotational point engaged and moved forward by the conveying chains, so that the workpiece is aligned longitudinally in the transport direction. When employing this apparatus, however, a relatively long distance has to be travelled in order to turn the workpiece moving forward in a flat position around an angle of 90.degree..
An apparatus of the same species is known from German patent specification DE-PS 14 36 856, in which the workpieces, of which initially the narrower side edge is conveyed as the front edge, are turned 90.degree. such that, after passing through the apparatus, the wider edge is conveyed as the front edge. According to this prior art, the workpiece is gripped by corresponding clamping elements of conveying chains circulating one above the other in a vertical plane, and held in the vicinity of a front corner for further transport. Several conveyor belts run in parallel next to the conveying chains, each of said parallel conveyor belts exhibiting an increasingly high circulating speed as the distance from the conveying chains increases. In this way, the workpieces, which are only held between the clamping elements pivot-mounted on the conveying chains, are simultaneously rotated during the onward transport by the differential speed of the parallel conveyor belts, preferentially by 90.degree., so that finally the longer side edge is at the front in the direction of travel. With this prior art apparatus, each conveyor belt driven at a relative speed compared with the conveying chain pair must be operated via a correspondingly designed gear unit. Such an apparatus is not only complicated but also requires a high level of maintenance and is susceptible to malfunctioning.
The object of the present invention is to further develop an apparatus of the same species such that it exhibits a comparatively simple design and is as compact as possible.